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Antioxidants, nature and chemistry

 Submitted by Dr. Tamer Fouad, M.D.

Classification of major antioxidants

Table 2 Classification of major antioxidants

Enzymes

Antioxidant

Role

Remarks

Superoxide dismutase (SOD)

Mitochondrial

Cytoplasmic

Extracellular

Dismutates O2? to H2O2

 

 

 

Contains Manganese (Mn.SOD)

Contains Copper & Zinc (CuZnSOD)

Contains Copper (CuSOD)

Catalase

Dismutates H2O2 to H2O

Tetrameric hemoprotein present in peroxisomes

Glutathione peroxidase (GSH.Px)

Removes H2O2 and lipid peroxides

Selenoproteins (contains Se2+)

Primarily in the cytosol also mitochondria

Uses GSH

Vitamins

Alpha tocopherol

Breaks lipid peroxidation

Lipid peroxide and O2? and ?OH scavenger

Fat soluble vitamin

Beta carotene

Scavenges ?OH, O2? and peroxy radicals

Prevents oxidation of vitamin A

Binds to transition metals

Fat soluble vitamin

Ascorbic acid

Directly scavenges O2?, ?OH, and H2O2

Neutralizes oxidants from stimulated neutrophils

Contributes to regeneration of vitamin E

Water soluble vitamin

-Modified from Fisher, 1988.

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